It has been proposed to deliver certain types of drugs to patients by inhalation of a powder as a delivery mechanism. An inhaler having a replaceable cartridge or capsule containing the drug powder is used for drug delivery. The administration of drugs by inhalation typically requires a very small quantity of powder in the inhaler cartridge. By way of example, application of insulin using Technosphere® microparticles can require a dose of as little as 10 milligrams of the powder. In addition, the drug dose must be highly accurate. A dose lower than specified may not have the desired therapeutic effect, while a larger than specified dose can have an adverse effect on the patient. Furthermore, while Technosphere microparticles are highly effective for drug delivery by inhalation, their platelet surface structure causes Technosphere powders to be cohesive and somewhat difficult to handle.
In the commercialization of drug delivery by inhalation, large numbers of cartridges containing the drug must be produced in an efficient and economical manner. An accurate dose of powder must be delivered to each cartridge, and the drug dose in each cartridge must be verified. Manufacturing techniques and equipment should be capable of high throughput to meet demand and should be capable of handling powders which are cohesive and thus do not flow freely. Existing manufacturing techniques and equipment have not been adequate to meet these demands.
International Publication No. WO 2007/061987, published 31 May 2007, discloses systems and methods for simultaneously dispensing precisely-controlled doses of a powder into multiple cartridges. The powder can contain a drug, and the cartridges can be used in inhalers. The fill state of each cartridge, typically the powder weight, is sensed during filling, and powder dispenser modules are individually controlled in response to the sensed weight to insure accurate dosage. The system operates at high speed and can be very compact to enable production filling operations with minimum floor space requirements. Nonetheless, there is a need for improved methods and apparatus for powder dispensing.